Automotive vehicle body structural members and other articles of manufacture may be made by bending (if necessary) and expanding at least portions of a metal tube against one or more restraining and shaping dies. An example of such a structural member is a body frame rail. When metal tubes are formed into desired articles, a length of tubing at each end may have an irregular shape and therefore may be discarded as scrap metal. It would be desirable to reshape the tube ends as part of the article to reduce wasted metal.
One example of a forming process for metal tubes is hydroforming. Conventional tube hydroforming requires that the ends of the metal tube workpiece be attached and sealed to an apparatus that fills the tube with highly pressurized fluid needed to expand the tube to fill a die cavity. The tube is filled with water or other fluid, and water pressure or other fluid pressure is applied to the inside of the tube to expand it against forming surfaces of a shaping die or mold. The tube may be straight or bent to achieve a desired shape such as that of a vehicle body rail.
Thus, a length of tubing at each end of the part used for this attachment cannot normally be shaped by the die or become part of the finished hydroformed part. There is also typically a length of tube described as a transition zone, further away from and not directly attached to the pressurization apparatus, which is also partially constrained from being fully formed into the die cavity to the finished part shape. After hydroforming the tube, the combined length of material comprising the transition zone and attachment length, which in some cases is about 300 mm long, are removed from the as-formed tube as engineered scrap. In the manufacture of a substantial number of hydroformed parts considerable tube metal must be removed and discarded. After the length of material comprising the transition zone and attachment length is removed, the hydroformed part may be subjected to secondary post-forming operations such as trimming the edge of the part, piercing holes in the part, or the like.
There is a need to utilize such end portions of metal tubes in the formed part instead of removing and discarding them.